Liquid pump



Aug. 13, 1968 13 INVENTOR.

A TTOR/VE Y United States Patent ice 3,396,663 LIQUID PUMP Thomas A. Bratten, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Sept. 15, 1966, Ser. No. 579,620 6 Claims. (Cl. 103-42) The invention relates to a liquid pump with a pump output pressure control mechanism. It further relates to a liquid pump with an integral pressure regulator and more particularly to one in which the regulator relieves the load on the pump when the desired pre-set pressure is achieved at the pump outlet. In addition, features are incorporated which prevent hunting of the regulator upon actuation, provide for a snap action, and insure that the regulator is free from leakage during the unloaded mode of operation while providing minimal friction during actuation. In the preferred embodiment the pump is an oil pump, and will be so described, although the invention may be utilized in pumps which pressurize other liquids.

In the drawing:

FIGURE 1 is a schematic cross section view of an oil pump embodying the invention, and

FIGURE 2 is a cross section view with parts broken away of a portion of the oil pump of FIGURE 1 and taken in the direction of arrows 22 of that figure.

The pump assembly 10 has a housing 12 in which the pump drive shaft -14 is rotatably mounted in suitable bearings 16 and 18. The portion of the shaft extending outwardly of the housing 12 is sealed by seal 20. The chamber 22 in which the shaft is positioned forms the pump sump. The inner end of the shaft 14 is formed to provide an eccentric cam 24. A bore 26 in the housing connects with the sump chamber 22. A plunger 28 is reciprocably mounted in bore 26 with one end being formed as a cam follower 30 which engages cam 24, and the other end acting as a pump piston 32. One end of a compression spring 34 engages a shoulder on the housing through which bore 26 extends. The spring surrounds the plunger 28, with the other end engaging the cam follower 30- so that the plunger is urged toward the cam 24 and therefore follows the cam during cam rotary movement. The portion of bore 26 beyond piston 32 forms a chamber 36. A cross passage 38 intersects the chamber 36. The end of chamber 36 opposite piston-32 has a discharge passage 40 connecting to another cross passage 42. A ball check type of discharge valve 44 normally seats in the end of passage 40 and is urged into the seated position by a spring 46. Another cross passage 48 extends through chamber 36, as is better seen in FIGURE 2. This passage is connected to the inlet port 50 and to a passage 52 which is connected to the sump chamber 22. A valve seat 54 is formed in passage 48 adjacent chamber 36 and a ball check valve 56 is urged against the seat by spring 58. This spring is mounted on a pin 60 which is formed as a part of a plug 62 closing the outer end of passage 48 opposite valve seat 54. A downward motion of the plunger 26 under influence of spring 34 creates a partial vacuum in chamber 36 and causes oil to be drawn in through inlet port 50 and valve 56. An upward stroke of the piston pressurizes the fluid so drawn into the chamber 36 and forces it out through passage 40, discharge valve 44, and into passage 42. One end of passage 42 is connected to the outlet port 64 which leads to any suitable mechanism utilizing the pressure so produced. The other end of passage 42 connects with a chamber 66 formed in housing 12. A plunger 68 is reciprocably received in a bore 70 which connects with chamber 66. The plunger 68 has an enlarged head 72 in chamber 66 which is engaged by spring 74, urging the plunger downwardly toward the sump chamber 22. The bottom of chamber 66 has a seal 76 received therein about the plunger stem 3,396,663 Patented Aug. 13, 1968 78 so that the plunger head 72 can engage the seal upon suflicient downward movement. The underside of the head 72 is formed as an annular valve seat 80, which actually engages the seal 76. The plunger stem 78 has an annular groove 82 formed therein which is engageable by a ball detent 84. Detent 84 is positioned in a passage 86 intersecting bore 70. A detent spring 88 urges the ball detent 84 into engagement with the plunger stem 78.

The lower end of the plunger 68 engages a piston 90 received in an enlarged bore 92 aligned with bore 70 and opening at the lower end into sump chamber 22. An eccentrically disposed axially extending passage 94 is formed through piston 90 so that it opens through the end of the piston adjacent plunger stem 78 and also through the end of the piston adjacent sump chamber 22. The bore 92 is connected with bypass passage 38 so that when the piston 90 is in the upward position shown, passage 38 is closed. The piston therefore acts as a bypass passage control valve. A pre-loaded spring 96 is held in bore 92 by a spring retainer 98 adjacent sump chamber 22 so that the spring urges the piston 90 and the plunger 68 upwardly. Spring 96 is stronger than spring 74 so that the spring forces tend to hold the plunger in the position shown in the drawing. In addition, the detent 84 is positioned within the annular groove 82 so that it also tends to hold the plunger in this position.

The pump output pressure in passage 42 is connected to chamber 66 where it acts on plunger 68 with a force determined by the cross section area of plunger stem 78. This force is transmitted through the stem 78 to piston 90 and is resisted by the pre-load on spring 96. Piston 90 will remain in the seated position shown so long as the pressure in chamber 66 is insutficient to overcome the pre-load on spring 96 and the resistance of ball detent 84. During this time some moderate resistance to fluid leakage from chamber 66 is provided by seal 76 and the fit of stem 78 on bore 70, although seal 76 is purposely a loose fit to prevent frictional resistance. When a suflicient predetermined pressure is built up in chamber 66 the force on plunger 68 overcomes the pre-load of spring 96 and the resistance of detent 84 so that the plunger is moved downwardly to unseat the piston 90. Since the resistance of the detent 84 will no longer act on stem 78 once the detent has been lifted out of annular groove 82, the pressure on plunger 68 will immediately drive the annular valve seat against the seal 76, thus achieving a substantially perfect seal of chamber 66 against leakage through bore 70. When the valve seat seals against seal 76, the fluid under the valve seat will promptly leak through the slight clearance of seal 76 and stem 78. The pressure in chamber 66 will then act on the larger area of the plunger head 72, rather than just the area of stem 78, thus noticeably increasing the force available to overcome spring 96 and likewise available to insure a tight seal between the valve seat 80 and the seal 76. At the same time, piston will uncover passage 38 and the pressure in chamber 36 will thus be released through communication with the sump chamber 22 by way of passages 38 and 94. The plunger 68 is therefore a part of the valve operating means for piston 90 in its valving action, and is more particularly a pump output pressure actuated means. Fluid communicated to the sump chamber 22 is also in free communication with the inlet port 50 through the passage 52.

When the pressure in chamber 66 falls below that which is suflicient to hold plunger 68 against the force of spring 96 with the assistance of spring 74, spring 96 will lift the valve seat 80 from the seal 76, at which time the area on which the pressure in chamber 66 acts will be reduced from that of plunger head 72 to that of the stem 78. Thus a noticeably lower force will then act, opposing spring 96, and the spring will therefore at once move g 3 piston. 90 to the seated position and chamber-36 will again be sealed for the pressurizing of fluid by the piston 32.

Thus by selection of the areas of plunger stem 78 and plunger head 72; the depth of the annular groove 82; the pre-load and strengths of springs 74, 88 and 96; and the diameter of the ball detent 84; the pressure at which the pump becomes unloaded and the pressure at which the pump again pumps can be varied and set for desired performance.

I claim:

1. A liquid pump having a liquid inlet and a pressurizing chamber and a pressurized liquid outlet, and further comprising:

a pump output pressure control mechanism including a bypass passage operatively fluid connecting said pressurizing chamber and said inlet, a bypass passage control valve selectively opening and closing said passage,

and valve operating means including;

pump output pressure actuated means urging said valve open,

and a yieldable force exerting means resisting valve opening movement of said output pressure actuated means,

said valve operating means further including a bore interconnecting said outlet and said inlet,

a plunger in said bore having an enlarged head on one end in said outlet and the other end engaging said valve for operation thereof by linear movement of said plunger in said bore,

and a seal substantially but incompletely sealing said plunger relative to said bore adjacent said enlarged head,

said plunger enlarged head being spaced from said seal when said valve is closed whereby said first eflective area is the cross section area of said plunger in said bore,

said plunger enlarged head having a seat thereon engaging said seal in substantially complete sealing relation when said valve is open whereby said second efiective area is the effective seat cross section area of said plunger enlarged head,

said pump output pressure actuated means having a first pump output pressure responsive effective area when said valve is closed and a second greater pump output pressure responsiveeffective area when said valve is open.

2. A liquid pump having a liquid inlet and a pressurizing chamber and a pressurized liquid outlet, and

further comprising:

a pump output pressure control mechanism including; a bypass passage operatively fluid connecting said pressurizing chamber and said inlet, a bypass passage control valve selectively opening and closing said passage, and valve operating means including pump output pressure actuated means urging said valve open and yieldable force exerting means resisting valve opening movement of said output pressure actuated means, said pump output pressure actuated means having a first pump output pressure responsive area when said valve is closed and a second greater output pressure responsive area when said valve is open, and including a linearly movable plunger having a detent groove formed therein,

said yieldable force exerting means including a ball detent in said groove and a spring urging said ball in said detent groove and yieldable upon the application of suflicient force moving said plunger linearly in the valve opening direction to allow said ball detent to be forced out of said groove, thereby substantially decreasing theresistance of said plunger to valve opening movement.

3. A liquid pump having a liquid inlet and a pressurizing chamber and a pressurized liquid outlet, and further comprising:

a pump output pressure control mechanism including;

a bypass passage operatively fluid connecting said pressurizing chamber and said inlet,

a bypass control valve selectively opening and closing said passage,

a valve operating means including;

pump output pressure actuated means urging said valve open, and yieldable force exerting means resisting valve opening movement of said output pressure actuated means,

said yieldable force exerting means including means first resisting valve opening movement of said pump output pressure actuated means at a high force level until the force exerted by pump output pressure on said first effective area exceeds said high force level,

and then resisting further valve opening movement of said pump output pressure actuated means at force levels substantially lower than said high force level throughout further valve opening movement and the valve hold-open position of said pump output pressure actuated means, said pump output pressure actuated means having a first pump output pressure responsive area when said valve is closed and a second greater pump output pressure responsive area when said valve is open.

4. The subject matter of claim 3,

said first and further resisting means including a spring loaded ball 'detent and a detent groove formed in said pump output pressure actuated means.

5. The subject matter of claim 3,

said first and further resisting means including a preloaded spring continually urging said valve and said pump output pressure actuated means toward the valve closed position.

6. The subject matter of claim 3,

said first and further resisting means including a spring loaded ball detent and a detent groove formed in said pump output pressure actuated means and pre-loaded spring means urging said valve toward the valve closed position.

References Cited UNITED STATES PATENTS FRED C. MATTERN, 112., Primary Examiner.

W. J. KRAUSS, Assistant Examiner. 

1. A LIQUID PUMP HAVING A LIQUID INLET AND A PRESSURIZING CHAMBER AND A PRESSURIZED LIQUID OUTLET, AND FURTHER COMPRISING: A PUMP OUTPUT PRESSURE CONTROL MECHANISM INCLUDING A BYPASS PASSAGE OPERATIVELY FLUID CONNECTING SAID PRESSURIZING CHAMBER AND SAID INLET, A BYPASS PASSAGE CONTROL VALVE SELECTIVELY OPENING AND CLOSING SAID PASSAGE, AND VALVE OPERATING MEANS INCLUDING; PUMP OUTPUT PRESSURE ACTUATED MEANS URGING SAID VALVE OPEN, AND A YIELDABLE FORCE EXERTING MEANS RESISTING VALVE OPENING MOVEMENT OF SAID OUTPUT PRESSURE ACTUATED MEANS, SAID VALVE OPERATING MEANS FURTHER INCLUDING A BORE INTERCONNECTING SAID OUTLET AND SAID INLET, A PLUNGER IN SAID BORE HAVING AN ENLARGED HEAD ON ONE END IN SAID OUTLET AND THE OTHER END ENGAGING SAID VALVE FOR OPERATION THEREOF BY LINEAR MOVEMENT OF SAID PLUNGER IN SAID BORE, AND A SEAL SUBSTANTIALLY BUT INCOMPLETELY SEALING SAID PLUNGER RELATIVE TO SAID BORE ADJACENT SAID ENLARGED HEAD, SAID PLUNGER ENLARGED HEAD BEING SPACED FROM SAID SEAL WHEN SAID VALVE IS CLOSED WHEREBY SAID FIRST EFFECTIVE AREA IS THE CROSS SECTION AREA OF SAID PLUNGER IN SAID BORE, SAID PLUNGER ENLARGED HEAD HAVING A SEAT THEREON ENGAGING SAID SEAL IN SUBSTANTIALLY COMPLETE SEALING RELATION WHEN SAID VALVE IS OPEN WHEREBY SAID SECOND EFFECTIVE AREA IS THE EFFECTIVE SEAT CROSS SECTION AREA OF SAID PLUNGER ENLARGED HEAD, SAID PUMP OUTPUT PRESSURE ACTUATED MEANS HAVING A FIRST PUMP OUTPUT PRESSURE RESPONSIVE EFFECTIVE AREA WHEN SAID VALVE IS CLOSED AND A SECOND GREATER PUMP OUTPUT PRESSURE RESPONSIVE EFFECTIVE AREA WHEN SAID VALVE IS OPEN. 